黄河沿岸海底地下水细菌多样性

　　海底地下水排泄(Submarine Groundwater Discharge，SGD) 是陆地和海洋交换营养盐，含碳化合物、金属离子等物质的重要途径之一，而微生物被认为是SGD途径中生物地球化学循环过程的重要参与者。本项目中，我们基于16S RNA Illumina Miseq 高通量测序技术，对我国黄海沿岸两种典型类型的海底地下水，即地下淡水（井水）和地下咸水（间隙水）的细菌多样性和分布进行了系统的研究。其中地下淡水样品采集于受人类活动严重影响的生态环境中，其细菌多样性远低于地下咸水，说明了人类活动造成的环境压力对菌群组成的影响。我们发现属于放线菌门和Beta-变形菌纲的细菌，特别是Comamonas和 Limnohabitan 这两个属的菌群是井水的优势菌群，而这两个属的细菌在间隙水中鲜少被检测到，表明这两类细菌更适宜淡水环境。据研究报导，Comamonas属的细菌已成功应用于污染环境的微生物修复中，我们发现在淡井水样品中存在大量与Comamonas属细菌高度相似的序列，预示此类细菌可作为候选菌，对高度污染的井水在进入沿岸区域前进行微生物修复，从而减轻对环境的负面影响。采集于不同旅游海滩的咸间隙水有其特征的菌群组成，比如，采集于远离藻华海域的间隙水中有丰富的蓝细菌，而在靠近藻华区域的间隙水样品中，我们检测到六类参与氮循环的稀有菌群。同时我们通过代表菌群和环境参数相关性的统计分析，发现这两类海底地下水向沿岸水体提供了不同的类型的营养盐。例如，井水中的Beta-变形菌纲细菌与铵盐呈明显的负相关而与硝酸盐呈高度正相关，而咸间隙水中的蓝细菌和铵盐呈高度正相关，说明了井水和盐间隙水可能分别向沿岸水提供了硝酸盐和铵盐。我们对黄海沿岸海底地下水细菌菌群结构的详尽分析和研究，为未来设计有效的微生物修复方法，现场净化和修复海岸带污染环境提供了理论依据, 对海岸带的开发和管理有重要意义。

FIGURE2 Heatmap showing the relative abundance and distribution of genus-based OUT illumine reads. The color code indicates relative abundance, ranging from blue (low abundance) to black to brown (high abundance).
FIGURE7 Environmental factors associated with variations of the bacterial community structure at the phylum level. In order to obtain a higher resolution, the Proteobacteria phylum level was separated into Alpha, Beta, and Gamma-Proteobacteria classes. Phylum Bacteriodetes was separated into classes Flavabacterria and Cytophagia. The total number of sequences in each phylum is indicated in parentheses. Pearson’s correlation coefficients between-1 and 1 are shown in the rectangle, which indicates correlations between phylum/class sequence abundance and selected environmental parameters. For example, afirebrick colored rectangle (0.76) between nitrate and Betaproteobacteria indicates a higher number of sequences within creasing nitrate concentration, a blue rectangle (−0.774) between Betaproteobacteria and ammonium indicates a higher number of sequences with decreasing ammonium concentration. The color code indicates Pearson’s correlation coefficients, ranging from blue(−1) to white (0) to firebrick (1). The density showed the distribution of Pearson’s correlation coefficients between −1 and1.Si, silicate; P, phosphate; NO2, nitrite; NO3, nitrate; NH4, ammonium; 224Ra, Radium isotope tracer; DOC, dissolved organic carbon.　　
　　

　　此研究结果已发表在微生物领域的国际权威杂志《Frontiers in Microbiology》上: